Embodiments described herein relate to the preparation and use of nickel-based catalysts in reducing carbon monoxide, hydrocarbon emissions, and nitrogen oxides (NOx) from vehicle exhausts, and more particularly, to a nickel-based catalyst used in a vehicle aftertreatment system to provide supplemental oxygen storage capacity for the oxidation of carbon monoxide and hydrocarbons, and the reduction of nitrogen oxides.
In recent years, government regulations in the United States have restricted emissions of carbon monoxide (CO), hydrocarbons (HC) and nitrogen oxides (NOx) from vehicle engine exhausts. This has necessitated the use of catalysts in gasoline-powered vehicles which function to stimulate the oxidation reaction of HC and CO and the reduction of NOx. Such catalysts are typically referred to as three-way conversion (TWC) catalysts because they simultaneously oxidize CO and HC to CO2 and water while reducing NOx to nitrogen. Three-way conversion catalysts often include materials with oxygen storage capacity (OSC), i.e., materials which provide additional oxygen needed to oxidize carbon monoxide and hydrocarbons in the exhaust at rich air/fuel ratios. During subsequent lean air/fuel operations, the excess oxygen in the exhaust then replenishes the depleted oxygen of the OSC materials used in the previous rich operations, which enhances the overall reduction of NOx in the exhaust stream.
Currently, OSC materials typically comprise cerium-based oxides such as cerium oxide (CeO2), cerium-zirconium mixed oxides (CexZryO2), and cerium-praseodymium mixed oxides (CexPryO2). However, in some vehicle operations with long and rich air/fuel excursions, conventional cerium-based oxides do not generate sufficient amounts of oxygen needed for the oxidation of HC and CO.
Accordingly, there is a need in the art for a catalyst which provides an oxygen storage capacity to meet the demand for oxygen in the reduction of carbon monoxide, hydrocarbon emissions, and nitrogen oxides from a vehicle exhaust.